FAQs on the Ongoing Gulf of Mexico Dolphin Die-off
What processes are under way to examine the potential effects of the Deepwater Horizon BP (DWHBP) oil spill on marine mammals?
There are multiple processes under way that are investigating the potential effects of the Deepwater Horizon BP (DWHBP) oil spill on marine mammals.
- Under the Oil Pollution Act of 1990, a Natural Resource Damage Assessment (NRDA) is being conducted. The NRDA is the process of collecting and analyzing information to assess the extent of injury to a natural resource and determining the appropriate type and amount of restoration needed to compensate the public for that injury. This includes assessing injuries to marine mammals, their habitat (or ecosystem), and the prey upon which they depend that may have occurred as a result of the DWHBP spill. The NRDA is being conducted by:
- National Oceanic and Atmospheric Administration (NOAA)
- U.S. Department of the Interior (DOI)
- U.S. Environmental Protection Agency (EPA)
- U.S. Department of Agriculture (USDA)
- The U.S. Justice Department is using investigations of these impacts for potential cases related to the DWHBP oil spill. As such, samples and all records/data collected from marine mammal strandings are considered potential evidence in these cases.
- Under the Marine Mammal Protection Act of 1972 (as amended), an Unusual Mortality Event (UME) has been declared for cetaceans (whales and dolphins) in the northern Gulf of Mexico (Texas/ Louisiana border through Franklin County, FL) from February 2010 through the present.
Given the overall complexity of the UME investigation and its overlap with and potential importance to ongoing legal investigations, all of the different investigative teams are coordinating their activities. This coordination ensures that all data and samples are collected, preserved, and stored appropriately, legally, and using the best scientific methods and are analyzed with the best available scientific tools so that they are useful to all parties interested in the health of marine mammals in the Gulf of Mexico.
An Unusual Mortality Event (UME) is defined under the Marine Mammal Protection Act as a stranding that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. There are seven criteria used to determine whether a mortality event is "unusual." If the Working Group on Marine Mammal Unusual Mortality Events (WGMMUME), a group of marine mammal health experts, determines that an event meets one or more of the criteria, then an official UME is declared.
19 UMEs have occurred in the Gulf of Mexico (12 of which involved cetaceans; the remaining 7 were specific to manatees only) since 1991, when the marine mammal UME program was established. More information on UMEs is available on our website.
- A recent paper compares the current UME to past dolphin UMEs in the Gulf of Mexico
- In the majority of previous dolphin mortality events in the Gulf, either morbillivirus or brevetoxicosis were suspected or confirmed as causal factors. Evidence to date does not support either morbillivirus or brevetoxicosis as a cause of the current UME
- The investigation is ongoing and no definitive cause(s) has yet been identified for the increase in cetacean strandings in the northern Gulf from 2010 to the present.
- Identification of spatial, temporal, and demographic clusters within the UME suggest that this mortality event may involve different contributing factors varying by location and time including a potential contributing role of the DWH oil spill on increased dolphin mortality following the spill.
Are there any preliminary results available at this time for the current UME?
Current results available from the UME investigation can be found here. NOAA will make every effort to make new data available to the public as soon as it is legally and scientifically appropriate and possible.
How many dolphins have stranded in the UME?
Please see the weekly updates on the Northern Gulf of Mexico UME website. Please note the numbers listed are preliminary and may be subject to change.
Since not all cetaceans that have died will wash ashore and be found, the number reported stranded is likely a fraction of the total number of cetaceans that have died during the UME.
What role does Brucella play in the UME?
- Brucella, a bacterium associated with flu-like symptoms in humans, but abortions in cattle and other mammals, has been identified in some bottlenose dolphins that stranded in the northern Gulf since the start of the UME.
- While Brucella has been confirmed in many marine mammal species globally, to date it has not been confirmed as causing epizootics or die-offs of multiple age classes in marine mammals, including dolphins.
- Brucella testing for the NGUME is ongoing. Additional analyses have been done to further understand the potential role of Brucella in the NGUME and throughout the US coastal waters. Results from these analyses will be forthcoming.
- Please see the CDC website for more information and our Marine Mammal Brucella fact sheet [pdf].
In general, throughout the region, strandings have been high for all age classes of dolphins. While it is typical to see a peak in strandings of premature, stillborn, and neonatal dolphins (<115cm) in the spring in the northern Gulf of Mexico, the peak observed in 2011, particularly in Mississippi and Alabama, was higher than expected.
What are the goals of the UME investigation?
There are four goals of any UME investigation, to:
- minimize deaths;
- determine the cause of the event;
- determine the effect of the event on the population; and
- identify the role of physical, chemical, and biological environmental parameters in the event.
NMFS and our Marine Mammal Stranding Network partners have been working throughout this event to collect samples using consistent protocols, archive and preserve samples using chain of custody protocols, and have submitted appropriate samples, as needed, to laboratories.
Have samples collected from marine mammals been analyzed already?
Throughout the oil spill response and UME investigation, some samples were held at the facilities where they were collected, some were shipped for analyses, and others were shipped to be archived until information gained in the investigation indicates that further analyses are needed.
To date, some samples have been submitted for analysis, including:
- blood analyses for live animals
- analyses needed for care of live animals
- formalin fixed tissues for histopathology
- tissues to test for morbillivirus, Brucella, and marine biotoxins
- swabs from externally visibly oiled animals for oil confirmation and fingerprinting
- bacterial cultures for pathogen identification from fresh carcasses or live animals
- genetic analyses
- PAH analysis
- Stable isotope analysis
- Teeth for aging of animal
- Stomachs for prey analysis
- records for review of gross findings
Data, record, and sample inventories are being catalogued following chain of custody at each Stranding Network facility, and samples are being shipped to either laboratories for analyses or to the National Marine Mammal Tissue Bank for archiving until such analyses are needed in the investigation. Original data records and photographs are being shipped to the NMFS Laboratory in Miami for review and archiving.
Due to the destructive processes used during chemical analyses, samples may be archived while methods are developed and/or decisions are made by the UME investigative team on those tissues and those methods needed.
Given the state of decomposition of many of the carcasses, initial evaluations of the viability of the samples for specific analyses is being done before they are submitted for chemical or some biological analyses. Sample shipment to laboratories will continue as new carcasses come in.
The investigative team is taking a tiered approach relying on pathology and epidemiology to guide the direction additional analyses may need to go as we rule in or out physical, chemical or biological factors that may be contributing to or causing these mortalities.
Many of the carcasses have been moderately to severely decomposed, which significantly reduces the ability to perform many analyses. Some sample analyses are not possible given the decomposition of the carcasses.
Is NMFS/NOAA also evaluating live marine mammals in the northern Gulf?
It is crucial that the UME investigative team evaluates what is going on with live cetaceans in areas where elevated strandings have occurred. As such, the UME investigation benefits from ongoing NRDA studies on live animals in coastal areas of the northern Gulf.
Shortly after the oil spill response was initiated, the NRDA process for marine mammals began (early May 2010). Under the NRDA, a variety of studies are being conducted to try to determine potential impacts from the spill on marine mammals. These studies have focused on understanding the type, severity, magnitude, and duration of exposure of oceanic, coastal, and estuarine marine mammals to oil.
One study found a high prevalence of lung disease and evidence of hypoadrenocorticism (low functioning of the adrenal gland which altered stress response) in live bottlenose dolphins in Barataria Bay, Louisiana. These abnormalities are consistent with adverse health effects previously documented in mammals following oil exposure.
These studies are ongoing and will likely continue for some time until we understand what impacts may have occurred. Additional information on NRDA marine mammal studies can be found here:
- Natural Resource Damage Assessment for the Deepwater Horizon/BP Oil Spill:
- NOAA conducts dolphin health assessment in Barataria Bay, Louisiana
- Study by NOAA and Partners Shows Some Gulf Dolphins Severely Ill
Where can I find additional information on UMEs?
- Northern Gulf of Mexico UME
- Participants in NOAA's National Marine Mammal Stranding Network
- Marine Mammal UMEs
- National Contingency Plan for Response to Unusual Marine Mammal Mortality Events [pdf]
- Working Group for Marine Mammal UMEs
Updated: February 12, 2015